Any Amazon workers?

Hi, I've got a question about Amazon returns. How do you know if you've purchased an item sold as 'new' that has been returned. I read that an LPN barcode is placed on an item. I bought some teething toys for my baby and this barcode was on the back. Surely it's not been returned and resold, it's unsanitary because it's a teething toy. I washed it and sterilised it before I gave it to my baby but then noticed the label on the back after he's had a good chomp on it. Am I just being an anxious, paranoid mum 🫣